1. Field of the Invention
This invention relates to polymeric hydroquinones which are especially useful as antioxidants in edible materials such as foods.
2. The Prior Art
The prevention or reduction of oxidation is important to the quality and life of a wide range of materials such as plastics and rubbers. Oxidation is an especial problem with consumable (edible) materials, as such oxidation not only can destroy desirable nutritional values in these materials, but also can render these materials unpalatable and unfit for consumption. A variety of materials have been proposed as additives to inhibit undesired oxidation. A common class of such materials have a phenolic or hydroquinolic structure. BHA (butylated hydroxy anisole) and BHT (butylated hydroxy toluene) are two of the most commonly employed antioxidants in edible compositions. While BHA and BHT have never been proven to be significantly toxic, allergenic responses have been observed and their use in foods has often been opposed. Upon ingestion with food, they pass through the gastrointestinal tract walls into the systemic circulation where they are metabolized into products whose identity and safety are not proven.
It has been proposed by Alejandro Zaffaroni, in his United States patent application Ser. No. 367,971, now U.S. Pat. No. 3,994,828, to avoid these toxicity questions of conventional antioxidants by fixing the antioxidant moieties to a controller molecule which is of a size which precludes its passage through the walls of the gastrointestinal tract. Such an approach does work and it is possible to essentially completely prevent the passage of antioxidant moieties into the systemic circulation by incorporating them into nonabsorbably-large molecules. This technique has additional benefits in that the antioxidant molecules, being large, are not susceptible to undesired movement -- either migration in a substrate or volatilization from a substrate, benefits which substantially improve their usefulness not only in foods but also in non-food applications.
A substantial number of these polymeric antioxidants have been prepared. Some are similar in antioxidant activity to the conventionally used monomeric BHA and BHT materials, but as a rule, they were not markedly superior in their antioxidant activity to these prior materials.
Knowing from the art that the hydroquinones are an attractive family of antioxidants, various polymeric hydroquinone antioxidants were investigated.
Materials having a structure ##STR2## wherein X is a leaving group and R is a lower alkyl, were prepared by reacting poly(X-methyl styrene) with the required hydroquinone in the presence of a cationic catalyst. These materials were of relatively unimpressive antioxidant activity. Further study of this reaction scheme failed to yield materials of antioxidant activity higher than that observed with conventional monomeric BHA and BHT.
It is thus a primary object of this invention to provide to the art a polymeric hydroquinone antioxidant with a molecular size suitable for substantial nonabsorbtivity from the gastrointestinal tract and antioxidant activity superior to conventional BHA and BHT antioxidants.